CGRG Bibliography of Canadian Geomorphology
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Author : Chutko, K.J.; and Lamoureux, S.F.
Date : 2007.
Title : Development of a organo-clastic sediment deposition model for a High Arctic coastal lake.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
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Abstract
An unusual and long record of laminated organic and clastic sediments was recovered from a small coastal lake on the Colin Archer Peninsula, Devon Island (76°12’N 90°47’W). The sediment core was 4 m long, with a distinct transition in the upper 1.96 m. Based on the inferred sedimentology and a 14C date, this transition was interpreted to represent the post-glacial emergence of the lake from the marine environment (ca. 4000 BP). Organic matter accumulation occurred after emergence and has continued to the present. Based on two surface sediment cores, three sediment types were identified in the laminated record: clastic material composed dominantly of detrital carbonate sediments, and two types of organic matter. The organic components were distinguished based on colour and relative texture, and were inferred to represent distinct periods of either bacterial growth or algal sedimentation. The typical sedimentary rhythmite was composed of three distinct units. A normally graded clastic unit forms the base, and ranged in thickness from < 100 µm to > 5 mm. The clastic units contained varying amounts of detrital (likely terrestrial) organic matter within each, and in many cases were dominated by the organics. Second, a unit of red organic matter was deposited on top of the clastic unit. These units often accumulated as multiple laminae, and were therefore inferred to be cyanobacterial mats. Finally, a layer of yellow organic matter accumulated on top of the bacterial mat unit. These units were relatively featureless, and did not vary considerably in thickness (< 100 ?m). These units were interpreted to be accumulations of algae. In most cases, conformable contacts between the units were observed. Though the existence of annual rhythmicity cannot be confirmed at this time, the relatively simple arctic depositional environment and the inferred strong seasonality of the three units suggests that these sediments may reveal a complex annual signal of clastic and organic sediment accumulation. We are undertaking detailed sedimentary, SEM, pigment and related analyses to further characterize the composition of the sequence. While known to exist in Antarctic lakes, microbial and algal accumulations are not reported for High Arctic lacustrine environments. The long record (ca. 4000 years) from this lake provides a unique opportunity to understand long term patterns in High Arctic lake productivity, as well as an increased understanding of the physical processes which may influence microbial and algal growth in this environment.
Bibliography of Canadian Geomorphology